Scientists have been researching the parasitic relationship between grasshoppers and the nematomorph hairworm (Spinochordodes tellinii). The hairworm lives and breeds in fresh water, but spends a part of its life eating the insides of live grasshoppers and then brainwashing the grasshopper into committing suicide by hopping into a pool of water and drowning. The hairworms, several times the length of the grasshopper at the time of the unfortunate incident, then emerge and continue their lifecycle in water. A team of researchers at the French National Center for Scientific Research is studying just how the hairworm manages to take over the body of the grasshopper.

This is just one example of a parasite seemingly taking over its host to produce specific results. In Costa Rica, there is a wasp whose larva lives inside the body of an orb-weaving spider. The evening before the larva kills the spider, the larva somehow manages to reprogram the web building activity of the spider so that it creates a durable platform for the larva to pupate on, instead of its usual temporary web. Studies show that if the larva is removed from the spider before the larva kills the spider, the spider will return to its usual web building activities within a couple of days.

And, if you think about it, the rabies virus makes animals so rabid that they want to bite others — which transmits the virus.

Your Comments, Thoughts, Questions, Ideas

Elsa says:

Today at a wading pool on our 4th grade field trip, I caught this preying mantis on a rock in the middle of the pool. When I picked it up, it jumped off my hands into the water and I quickly scooped it up again. A teacher came to see the preying mantis and while we were watching it, something blackish brown came out of its rear end. At first I thought it was feces, but then it started to wriggle around. It was about 10 inches long and very skinny. At first we thought it was some sort of tapeworm. We let the preying mantis go on a tree. We took the worm back to our school and asked a science teacher what it was. He said it was an Ascaris, but we looked on websites and saw that it was really a hairworm because it matched the definition and picture on this website. No one mentioned hairworms coming out of preying mantises so I was just asking you if that's normal.

Elsa, thanks for your question! I found several references to hairworms and praying mantises on the web, a couple specific to Japan, so it seems that this is indeed possible. I could not determine a specific species that uses praying mantises as the vector. According to Wikipedia, there are about 320 species of hairworms.

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